The present invention relates to a cross frog for switches and crossings, including a cross frog tip and, extending at both sides thereof, wing rails and running rails having a basic shape aligned with a main or branch track.
In the field of rigid cross frogs, guide rails give rise to guidance problems, since a flange, in the vicinity of a cross frog gap, which is inevitably caused by intersecting flange grooves, cannot guide the wheel on the head of a rail. Depending on the width of the flange grooves, the axle, and thus the bogie of a vehicle, is joltingly deflected sideways by the guide rail. For trains which travel through a cross frog zone at a speed of e.g. 160 km/h, this deflection occurs in hundredths of seconds. These jolts, on one hand, reduce travel comfort, and on the other hand cause undesirable wear.
Due to constructional requirements, cross frog tips are formed extremely narrowly at their front zones, so that when they are encountered by a wheel, they are subjected to increased wear. This occurs to an extreme extent when the flange of a wheel, at the front zone of the cross frog tip, slides along the cross frog tip.
To avoid or reduce the running on the cross frog tips, according to EP 0 282 796 B1, there is an intentional extension of the transfer zone between the wing rails and the cross frog tip in order to avoid a sudden transfer of force at a point or a very narrow zone from the wing rails to the cross frog tip.
According to DE 42 24 159 A1, the guide rail and the cross frog are intended to extend as a unit from a common base, which is resiliently supported on a sleeper by an intermediate support having spring properties. In this way, on one hand, a preservation of the cross frog tip occurs and, on the other hand, an impact-like co-operation of the wheel and the guide rail is avoided.
Movable cross frog tips are also known, by which it is likewise be attempted to eliminate jolting encounters with the cross frog tip or a grinding of the flange along the cross frog tip.
The present invention is based on the problem of developing a cross frog of the first-mentioned type in such a way that a reduction of wear of the cross frog tip zone occurs without reconstruction of the cross frog tip itself or of the associated guide rail, or of their orientation relative to one another, being required.
According to the invention, the problem is solved, substantially, in that at least one of the running rails, particularly both running rails, deviates in the zone of the cross frog tip from its basic shape in such a way that the wheel- or bogie axle of a railroad vehicle travelling along the main or branch track experiences an effect of a movement directed away from the cross frog tip.
By the change of shape, the wheel rolling at the running rail side undergoes a change of its point of support such that the wheel- or bogie axle is forcibly aligned relative to the main or branch track so that the normal thereof extends parallel to or approximately parallel to the respective longitudinal axis of the track being travelled, with the consequence that the grinding or sliding movement of the wheel flange along the flank of the cross frog tip, which would otherwise cause wear, does not occur.
It is in particular intended that the change of shape of the running rail is so formed that a wheel travelling along the running rail is held to a running circle of radius r1, which is smaller than a running circle r2 to which the wheel rolling on the cross frog tip is held. The radii r1 and r2 are thereby related substantially as r1:r2≈0.91:1 to r1:r2≈0.98:1.
Differing from the above-mentioned state of the art, in the zone of the cross frog tip no new reconstruction of the cross frog tip itself or of the arrangement of the cross frog tip with respect to the guide rail occurs, but the running rails associated with the cross frog tip are so changed in shape that an intentional influence on the point of support of the wheel rolling on the running rail is produced, with the consequence that the wheel flange of the wheel rolling on the cross frog tip is held away from the flanks of the cross frog tip.
In particular, it is intended that the running rail, in the zone of the cross frog tip, with respect to its line of contact formed by the prevailing points of support of the wheel, runs curved away from the cross frog tip, and thus exhibits a concave shape with respect to the cross frog tip.
The line of contact between the wheel and the head of the running rail, deviating from the basic shape, can be obtained by the running rail head or the running surface thereof, in the zone of the cross frog tip, being more inclined relative to the cross frog tip, in comparison to the basic shape of the running rail. In that connection, the running rail or its running surface in the zone of the cross frog tip can be more strongly inclined to the cross frog tip, through an angle xcex1, than the running rail in the basic shape, where 1.5xc2x0 less than xcex1 less than 5xc2x0, and especially xcex1≈3xc2x0.
An optimum preservation of the cross frog tip is obtained when the change of shape of the running rail begins at a distance x before the cross frog tip, where 15,000-20,000 mm greater than x greater than 5000 mm. Furthermore, the change of shape should terminate at a distance y beyond the cross frog tip, where 18,000-23,000 mm greater than y greater than 8000 mm. The beginning and end, for the main and branch tracks, can differ from one another distancewise, but can also be the same. That depends essentially on the radius of a switch.
The invention is distinguished, in particular, in that the maximum change in the basic shape of the running rail, transversely of the main or branch track, amounts to 5 mm to 30 mm. By the relevant track widening, in a constructionally simple manner an effect on the wheel- or bogie axle can occur such that the wheel rolling off at the side of the cross frog tip cannot run laterally against the cross frog tip, without the required guidance itself being effected.